[PATCH v2 9/9] powerpc/pseries: HVPIPE changes to support migration

[Mahesh J Salgaonkar]

On 2025-08-12 15:57:13 Tue, Haren Myneni wrote:
> The hypervisor assigns one pipe per partition for all sources and
> assigns new pipe after migration. Also the partition ID that is
> used by source as its target ID may be changed after the migration.
> So disable hvpipe during SUSPEND event with ‘hvpipe enable’ system
> parameter value = 0 and enable it after migration during RESUME
> event with  hvpipe enable’ system parameter value = 1.
> 
> The user space calls such as ioctl()/ read() / write() / poll()
> returns  -ENXIO between SUSPEND and RESUME events. The user space
> process can close FD and reestablish connection with new FD after
> migration if needed (Example: source IDs are changed).
> 
> Signed-off-by: Haren Myneni <haren at linux.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/mobility.c    |  3 +
>  arch/powerpc/platforms/pseries/papr-hvpipe.c | 64 ++++++++++++++++++++
>  arch/powerpc/platforms/pseries/papr-hvpipe.h |  6 ++
>  3 files changed, 73 insertions(+)
> 
> diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
> index 62bd8e2d5d4c..95fe802ccdfd 100644
> --- a/arch/powerpc/platforms/pseries/mobility.c
> +++ b/arch/powerpc/platforms/pseries/mobility.c
> @@ -28,6 +28,7 @@
>  #include <asm/rtas.h>
>  #include "pseries.h"
>  #include "vas.h"	/* vas_migration_handler() */
> +#include "papr-hvpipe.h"	/* hvpipe_migration_handler() */
>  #include "../../kernel/cacheinfo.h"
>  
>  static struct kobject *mobility_kobj;
> @@ -744,6 +745,7 @@ static int pseries_migrate_partition(u64 handle)
>  	 * by closing VAS windows at the beginning of this function.
>  	 */
>  	vas_migration_handler(VAS_SUSPEND);
> +	hvpipe_migration_handler(HVPIPE_SUSPEND);
>  
>  	ret = wait_for_vasi_session_suspending(handle);
>  	if (ret)
> @@ -770,6 +772,7 @@ static int pseries_migrate_partition(u64 handle)
>  
>  out:
>  	vas_migration_handler(VAS_RESUME);
> +	hvpipe_migration_handler(HVPIPE_RESUME);
>  
>  	return ret;
>  }
> diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.c b/arch/powerpc/platforms/pseries/papr-hvpipe.c
> index bc3d1f0b4491..0edc1a29d64d 100644
> --- a/arch/powerpc/platforms/pseries/papr-hvpipe.c
> +++ b/arch/powerpc/platforms/pseries/papr-hvpipe.c
> @@ -27,6 +27,7 @@ static unsigned char hvpipe_ras_buf[RTAS_ERROR_LOG_MAX];
>  static struct workqueue_struct *papr_hvpipe_wq;
>  static struct work_struct *papr_hvpipe_work = NULL;
>  static int hvpipe_check_exception_token;
> +static bool hvpipe_feature;
>  
>  /*
>   * New PowerPC FW provides support for partitions and various
> @@ -233,6 +234,12 @@ static ssize_t papr_hvpipe_handle_write(struct file *file,
>  	unsigned long ret, len;
>  	char *area_buf;
>  
> +	/*
> +	 * Return -ENXIO during migration
> +	 */
> +	if (!hvpipe_feature)
> +		return -ENXIO;
> +
>  	if (!src_info)
>  		return -EIO;
>  
> @@ -325,6 +332,12 @@ static ssize_t papr_hvpipe_handle_read(struct file *file,
>  	struct papr_hvpipe_hdr hdr;
>  	long ret;
>  
> +	/*
> +	 * Return -ENXIO during migration
> +	 */
> +	if (!hvpipe_feature)
> +		return -ENXIO;
> +
>  	if (!src_info)
>  		return -EIO;
>  
> @@ -401,6 +414,12 @@ static unsigned int papr_hvpipe_handle_poll(struct file *filp,
>  {
>  	struct hvpipe_source_info *src_info = filp->private_data;
>  
> +	/*
> +	 * Return -ENXIO during migration
> +	 */
> +	if (!hvpipe_feature)
> +		return -ENXIO;
> +
>  	if (!src_info)
>  		return -EIO;
>  
> @@ -530,6 +549,12 @@ static long papr_hvpipe_dev_ioctl(struct file *filp, unsigned int ioctl,
>  	u32 srcID;
>  	long ret;
>  
> +	/*
> +	 * Return -ENXIO during migration
> +	 */
> +	if (!hvpipe_feature)
> +		return -ENXIO;
> +
>  	if (get_user(srcID, argp))
>  		return -EFAULT;
>  
> @@ -688,6 +713,44 @@ static int __init enable_hvpipe_IRQ(void)
>  	return 0;
>  }
>  
> +void hvpipe_migration_handler(int action)
> +{
> +	pr_info("hvpipe migration event %d\n", action);
> +
> +	/*
> +	 * HVPIPE is not used (Failed to create /dev/papr-hvpipe).
> +	 * So nothing to do for migration.
> +	 */
> +	if (!papr_hvpipe_work)
> +		return;
> +
> +	switch (action) {
> +	case HVPIPE_SUSPEND:
> +		if (hvpipe_feature) {
> +			/*
> +			 * Disable hvpipe_feature to the user space.
> +			 * It will be enabled with RESUME event.
> +			 */
> +			hvpipe_feature = false;
> +			/*
> +			 * set system parameter hvpipe 'disable'
> +			 */
> +			set_hvpipe_sys_param(0);
> +		}
> +		break;
> +	case HVPIPE_RESUME:
> +		/*
> +		 * set system parameter hvpipe 'enable'
> +		 */
> +		if (!set_hvpipe_sys_param(1))
> +			hvpipe_feature = true;
> +		else
> +			pr_err("hvpipe is not enabled after migration\n");

So we will end up in else condtion if destination partition does not
have hvpipe capability ?

Thanks,
-Mahesh.

> +
> +		break;
> +	}
> +}
> +
>  static const struct file_operations papr_hvpipe_ops = {
>  	.unlocked_ioctl	=	papr_hvpipe_dev_ioctl,
>  };
> @@ -731,6 +794,7 @@ static int __init papr_hvpipe_init(void)
>  
>  	if (!ret) {
>  		pr_info("hvpipe feature is enabled\n");
> +		hvpipe_feature = true;
>  		return 0;
>  	} else
>  		pr_err("hvpipe feature is not enabled %d\n", ret);
> diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.h b/arch/powerpc/platforms/pseries/papr-hvpipe.h
> index aab7f77e087d..c343f4230865 100644
> --- a/arch/powerpc/platforms/pseries/papr-hvpipe.h
> +++ b/arch/powerpc/platforms/pseries/papr-hvpipe.h
> @@ -11,6 +11,11 @@
>  
>  #define	HVPIPE_HDR_LEN	sizeof(struct papr_hvpipe_hdr)
>  
> +enum hvpipe_migrate_action {
> +	HVPIPE_SUSPEND,
> +	HVPIPE_RESUME,
> +};
> +
>  struct hvpipe_source_info {
>  	struct list_head list;	/* list of sources */
>  	u32 srcID;
> @@ -33,4 +38,5 @@ struct hvpipe_event_buf {
>  				/* with specified src ID */
>  };
>  
> +void hvpipe_migration_handler(int action);
>  #endif /* _PAPR_HVPIPE_H */
> -- 
> 2.43.5
> 
> 

-- 
Mahesh J Salgaonkar